This invention pertains to subscriber television systems and, more particularly, to those systems wherein the subscriber terminals include video recorders.
There have been proposed subscriber television systems wherein a central station is connected to a plurality of subscriber terminals by means of a closed circuit multi-channel link, for example, a multi-channel television cable system. In such systems, the viewer is given a menu of programs to select for viewing and the viewer pays a charge usually on a per month basis. While these systems are operating successfully, they do not handle the problem of unauthorized duplication of the material. In particular, with the advent of video cassette records and video disc systems, this unauthorized duplication can become a very simple process. Therefore, the system operator must resign himself to the fact that if he shows a prime entertainment program he suffers the grave risk of a duplication followed by the selling of pirated cassettes.
It is, accordingly, an object of the invention to provide apparatus which controls the playback of information from a video recorder so that if the playback is unauthorized the displayed information is unintelligible.